Method and machine for relieving cutters



3- I "E. WILDHABER 2,332,421

METHOD AND MACHINE FOR RELIEVING CUTTERS Filed April 17, 1941 4Sheets-Sheet 2 ERNEST WILD/W955? 3m entor Oct. 19, 1943.

' E. WILDHABER METHOD AND MACHINE FOR RELIEVING GUTTERS Filed April 17,1941 4 Sheets-Sheet 4 Snueritor ERNEST wan/1055,?

/ 7 attorney Patented Get. 19, 1943 METHOD AND MACHINE FOR RELIEVINGCUTTERS Ernest Wildhaber, Brighton, N. Y.,* assignor to Gleason Works,Rochester, N. Y., a corporation" of New York Application April 17, 1941,Serial No. 389,014 c1.51-50) 1 Claims.

1 The present inventionhrelates to the reliefgrinding of thesidesurfaces of face-mill gear cutter blades. 1 V I There are severaldifferent processes known for the relief-grinding or" the side surfacesof face: mill gear cutter blades. One of the most widely.

used is the axial relievingprocess in which the cutter blades arerelief-ground in their own head with a rotary grinding wheel byeilecting a rela tive helical motion between the wheel and head once foreach blade to be ground. Another process, which has been extensivelyemployed, is the so-called offset grinding? process. In this process,the blades, which are tobe relief-ground, are

mounted in a dummy head to extend in a direce,

tion generally parallel to the 'aXis of the dummy head but to benon-radial of that axis so that corresponding side surfaces at one side'ofthe blades will lie in a common surface of revolution coaxial of thedummy head, and the relieving operation is effected by simply rotatingthe dummy head to passthe side surfaces of theblades across the rotatingwheel.

In my c'o-pending application, Serial he. I

388,229, filed April 12, 1941,. now Patent N0.

2,308,734, issued January 19,.1943,1have disclosed a method ofrelief-grinding iace-millgear cutter blades, particularly bladeshavingjcur ved" profiles,,in which the blades are 'fmountd in, a:

dummy head so that they aretilted forwardfroin their cutting positionsand have their tip surfaces lying in a plane perpendicular to the axisof the dummy head,and in which the side surfa'ceof a blade is relief-ground by rotating the dummy head past a rotating grinding wheel whilesimultaneously moving the wheel-axially so as to com pensate for andchest the change in pressure angle which would normally result fromgrinding the blade in tilted position. I g Y The axial relief-grindingmethod-cannot be employed for the relief-grinding of blades'of zero or,very'lcw pressureangle. of offset grinding? cannot be employed for therelief-grinding of blades of curved profile or of the so-called Topremtype where each blade has a side-cutting edge of two difierent pressureangles. I

One object of the presentinventionis to provide a simple yet practicalmethod. for reliefgrinding face-mill cutter blades of zero or quite lowpressure angle. 1 i

, A further object of the invention is to provide a new and improvedmethod'for the relief-grind-, ing inan offset head of blades oi curvedprofile,

onbroadly, blades having profiles which at diifer;

The known method of such a Wide. range of use universal in character.

, that is, em-radial position; and

entjportions in the height of'the blades arefbf different inclinations,such as blades of the Tope f pe.

Another and mostimportant object of the present invention is to. providea relief-grinding" machine on which face-mill geari cutter blades may Ibe ground either according. to the processes of the present invention oraccordingft'o the process.

of my prior application above mentioned.

Still another object of the invention is to provide amachine forrelief-grindingiace-mill gear cutter blades on which practically anyknown process offlrelief-grinding such blades maybe practiced and whichaccordingly will be capable. as to be practically Other objects of theinvention will be apparent hereinafter from the specification andfromthe recital of the appended claims.

In thedrawingsz,

big. 1 is a part section, somewhat diagrammatically the construction ora race-mill gear cutter relieving grinder built ac-- cording to oneembodiment of this invention and illustrating the use oi this grinder inthe relieving orthe side surfaces of. the blades by the process ioi' mycopending application above mentioned.

big. 2 1s a somewhat diagrammatic vlew'sh'owing the type or mechanismemployed ontnis inacnineji'or reciprocating each grinding wheel; I j 3is a sectional View taken at right -angles to tneview crisis. 2 andiurtherillustratingthe mechanism for reciprocating a wheel;

rigs. l and oare'diagrammatic views further illustrating 'Llle,operation or the reciprocating mechanism; i

Bias. 6 to 12 inclusive are illustrating various" methods that may beem: played for relief-grinding race-mill gear cutter blades .on thepresent machine, where the blades;

are to be relief-ground intheirown head?" f Fig. 13 .is a fragmentaryplan view showing-the position or the blades when mounted in the r owngrinding oifface-niillgear cutter blades when the,

blades are-mounted in a dumm head'inpii'iset,

Figs. 2,0 and 21 are fragmentary diagrammatic plan views showing,respectively, how the blades are mounted inldifierent dummy headsfor.relief-1 grinding the outsid andinsidebiadesurlaces,

partplan View, showing diagrammatic views at W and W, respectively. Thework spindle of the machine is denoted at 25. Th bladecarrying head,which may be either the actual cutting head or a dummy head, is securedto this spindle by any known or suitable meansl The work spindle issuitably journaled in a support or head which is mounted on the base 35of the machinefor sliding adjustment in the direction of the axis of thework spindle. The grinding wheels W and W are secured to wheel spindles31 and 31, respectively. These spindlesare journaled in sleeves and 40',respectively. The sleeves 4|! and 40 are mounted in heads or supports 4|and 4|, respectively, for reciprocation axially of their respectivewheel spindles, and the wheel spindles are so mounted as to reciprocatewith their respective sleeves.v

The mountings and operation of the two spindles are identical and'onlythe mounting and operationof the spindle 31 willbespecifically-described. Parts employed in the mounting and operationof the spindle 31', which correspond to those employed for the spindle31, are denoted by the same reference numerals s used for the.

spindle 31 except that the numerals are primed.

The head 4| is mounted on a swivel'member 42 for linear adjustment in a.direction at right angles to the axis of the spindle 31. The swivelmember 42 is mounted on a slide 43 for angular adjustment about an axisX extending at right angles to the axis of the wheel spindle; The

slides 43 and 43" are mounted on the base 36 for lateral adjustmenttoward and from one another. 7

The sliding adjustment of the head on the swivel member 42 permits orvarying the setting 0f the wh'eel to compensate for change in itsdiameter. The angular adjustment of'the swivel member 42 on the slide 43permits of set ting the grinding wheel in accordanc with the pressureangle of the blade surface to be ground. The lateral adjustment of the'slide 43 on the base 36 permits of spacing th grinding wheels inaccordance with the diameter of'the head in which the blades mounted. e

The wheel spindle fil is driven from a motor 45 that is mounted onthehead 4|. 'Thedrive is through th e pulley 46, belt 41 and pulley 48. Thepulley 46 is mounted I of the motor 45, and the pulley 48 has a splinedconnection with the wheel spindle 31. w In Fig. l, themachine is shownarranged for relief-grinding by the process of my prior applicationabove mentioned the side sin-races of blades Biiof v ter. For thispurpose, the blades are'mounted in a dummyhe ad 28 so that they aretilted forwardly out of cutting 'position' by the amount of the topclearance angle of the blades, and the tips of the blades all lie'i'n'aplane perpendicular to the axis of the work spindle 25'. The wheel W forgrindin th outside surfacesz'l of the blades is dressed to concavecircular arcuate prothat are to beground are on the armatur shaftaspherical type raeemm" gear cut file shape, while the blade W forgrinding the inside surfaces 23 of the blades is dressed to convexcircular arcuate profile shape.

For the relief-grinding operation, the work spindleZS is rotated on itsaxis past the rotary grinding wheels while the wheels ar reciprocatedaxially. The axial reciprocation is efiected in time with the rotationof the work spindle, and, during a revolution of the work spindle,occurs once for each blade to be ground. The axial movement of eachwheel is in one direction duringv actual di g of a side surface of ablade and in the opposite direction, when the relieving action iscompleted, in order to return the wheel to initial position ready forrelieving the next blade.

In the machine illustrated, the axial reciprocation of the grindingwheels is effected by movement of the sleeves 40 and 4a axially in theheads 4| and 4|. The reciprocatory movement of the sleeve 40 is producedby a cam 50 (Figs. 2 and 3) whichis mounted to rotate on the axis X. Theperipheral surface of the cam engages a bar 5| which is pivotallymounted at its two ends on pin 52 and 53, respectively, which arecarried by arms 54 and 55, respectively. The arms 54 and 55 arejournaled in the head 4| by integral trunnions 56 and 51, respectively.

Mounted on the arms 54 and 55 for sliding adjustment thereon are plates58 and 59, respectively. Pivotally connected to the plates 58 and 59 bymeans of pins 60 and 6|, respectively, is a bar 62. This bar is adaptedto engage between two lugs 63 and 64 formed integral with the sleeve 40.With the construction described, as the cam 50 rotates, Sliding movementis imparted to the sleeve 40 to reciprocate th sleeve in the head 4 I.

The bars 5| and 62 are parallel to one another and through their pivotalconnections form a parallelogram type linkage.

As illustrated diagrammatically in Fig. 4, as the cam 55 rotates on itsaxis, the arms 54 and 55 are moved about the trunnions 56 and 51 fromthefull line positions shown in thi figure to the dotted line positionsdenoted at 541 and 551, respectively,;and the bar 5| is thus moved fromthe full line position, shown in this figure. to the dottedline'position 5|1. Now during this movement of the bar 5| from full lineposition to the dotted line position denoted at 5h, the bar 62 will also'be swung about the trunnions 56 and 51, a shown in Fig. 5, moving fromthe full line position, denoted at 62 to the dotted line position 521.It will be noted, however, that since the bar 52 is at a smallerradial-distance from the trunnions 55 and '51 than the bar 5|, the bar62 will have a smaller amount of displacement than the bar 5L. Thuswhile the cam 51! moves the bar 5| the distance between the positions 5|and 5h, the actual axial movement transmitted to the sleeve 40 will bethe distance between the full line position at 62 and the dotted lineposition at $21 of the bar 52. By slidably adjusting the plates 53 and59 on'the arms 54 and 55, respectively, the amount of movement of thebar 52 can be adjusted, and thereby the stroke of the wheel Spindles 31and 3'! can be varied.

The two cams for reciprocating the sleeves 40 and 40 are driven in timewith the rotation of the work spindle a already described. The timedrelation of these several parts may be derived from a shaft H1, whichmay be driven from any suitable source of power. The shaft 10 may drivethe workspindle 25 selectively in either direction I ter shaft.

profile. iii are employed for grinding the outside and through the-bevelgears l l -and 13 or the bevel gears m ans 13 through engagement of theslidi3 is secur'edto' a shaft 159 There is a spur gear it secured tothecuterendof the shaft 15;"and this spur-gear forms one of a setofychange gears', of which 'the other members are denoted at 1-1; 18'and '19; These spur gears s'erve totransmit power -from the shaft 'i5 toa shaft 86, the spur gear '19 beingsecured to the upper endof this lat-There is atbevel gear BI secured to grinding'the inside surfacesof-blades iZil'of a Toprem type cutter. The'inside surfaces of 1such blades have al double pressure angle',th at is, the'lowerpart ofthe inside blade-profile is inclined at one angle to the axis of thecutter and the upper partis" inclinedto said axis at a different andlesser angle. Forthe grinding of the lower end of the shaft 8i! whichmeshes with a bevel gear that is fastened to a shaft v82. There is aworm .83integraljwith the shaft 82 .andthis a.

worm meshes with a. worm wheel 84 whichwis keyed or otherwise'secured.to the-work spindle .Mounted on state it this pair .of hl l oid pinions;90, .andfifl. These .mesh with the..hy=

poid' gears ti, and 9!,yrespectivelmwhich are secured to shafts Q2 and92, respectively, on whichthe ontrol cam 50 for the sleeve '40 and itscounterpartljor the sleeve dtiflrespectively, are mourlted.

; hrou h t e intestate."dat'rittd;tat; at

blade-carrying headlfi may be rotated in time with; the axialreciprocation of the sleeves ii] such loladl-zsga-grinding wheel I22 maybe employed which is dressed to adoubl'e pressure angle correspondih'gto the prcfileshap'e of the inside surfaces to be ground. The wheel isdressed to one pressure angle for the portion l23-of 'its height and toa different and lesser pressure an-' g le for'the portion I24 of it'sheight, the' difference in.pressure;angles for the two partsof the wheelprofile correspondingto'the difference in pressureangle's betweenthe'lowe'rand the upper portions ofthe inside surfacescf theblad'es. Thewheel is adjusted so that it'saxis R25 is parallel to the axis NH of the'blade car'rying head I02. Relief-grinding is effected. by rotating thewheel and 'head on their respective axes while recip wheel- 'i's movedaxially in onedirec'tion-during n a d h i ji gwheels m y be. r tated ontheir gwn axes in engagement with the sides V blades, to effect therelief-grinding oper- I ation."

re'ction when-the blade has been relieved to re froniitherelief-grinding method copending applicationabove mentioned, the machineof the present invention may be employed I for practicing a wide varietyof processes for relief g r inding 'face-rnill gear cutter blades.scmeor the methods which may be employed on therelieving machine of thepresent invention are illustrated diagrammatically in 'Figsrd toZlinclusive. I 1 J 1-,,

Figs. 6 to 12 inclusive illustrate various methods of relief-grindingthat may be employed where the cutting blades are ground in their'ownhead. In the several relief-grinding. processes. illustrated in thesefigurest theblades "B are mounted, as illustrated in' Fig. '13, in slots1.00

which are radial "or .theaxisifl l of the blade carrying head 1 m2,andthe blades Bextendin the directionof the BQXiSflfl l. :Fig. 1 3 showsfonly va fragment-of the head H32, anda'single'blade .B

' vention, it is possible, however, to produce 'a' mounted therein. Theslots I06 ateither'side of the slot; in which 'the' "blade is munteafi'are empty for ordinarily only alternateblade 'ican be ground'atone time.

Fig; 6*shows one way which th machine may be employed for axiallyrelieving -the side surfaces of'blades 105 whose outsideand inside"surfaceslet and I01, respectively, are of straight inside surfaces;respectively, of the blades, and

the swivel members :32 and 42 are adjusted-so" Here conical grindingwheels H0 and" that-.theaxesiiZ and H3, respectivelyjo'f"the wheels willbepai-allel to theaxis *lill ofthe, blade carrying head M2. Therelief-grinding0p erationis effected by rotating the wheels ontheiraxes,and the head on itsaxis it] while reciprorocatingthewheelinthe directionof its axis; as 1 indicated; bythe' arrow i28, once perblade to be ground'on a revolution of the headfHIZ. The

the felieving of a] blade and the opposite diturn the wheel to initialposition ready for the grinding'ofthe-next blade; While' Fig fl'illustrates'the relief-grindingef inside blades ofthe 1 Toprem type, itwill be understood that outside blades of this type may be similarlyrelieved.

Fig. dillustrates 'a novel -method, which may be" practiced onjthemachine of the present invention-,for= therelief-grinding of bladeshaving side surfaces of zero or low pressure angle.

The bladesifltshownin the drawings have outside surfacesl3l ofzero'pressure'angle extending parallel'to the axis fill of the'hfead H32in which the blades are mounted. It will be obvious that such side;surfaces" cannot be axially relieved,

for axial relief would not produce any cutting clearance. Withthemachine'of the present incombined axial and radialrelief in' a-single oderation which will provide sufiicient cutting clearance'. Such reliefmaybe achieved by using a conical 'g rinding wheel such as shown at I35.Thewheel is dressed at suohan angle that its effective profile willextend-parallel tofthe axis Nil ofthe blade-carryinghead, that is,willex tend in the direction of the profile of the blades to be ground.The axis 138 of the wheel will therefore be inclined to the axis it! ofthe cutter head. jl lence, when the'whe'el isnioved axially asden'otedby the arrow !31, there will be a componentbf this motion in 'adirection radial of theaxis ml of-the cutter head. H m the iasurfa'ces'gmund on -the blades will have a'con bined axial and-radialrelief. As before, the,

wheel and head are rotated on their'axes-and thewheel is reciprocatedaxially in time with the head rotation once for each blade to be ground,The movement of the wheel will be in one direction duringthe actualgrinding of the blade and in" the opposite direction'when aside sur facehas beenrelieved, in order to return the wheel I to initial positionready for the grinding of the next blade. v

Fig. 9' shows, the novelmethod as applied to the relief-grinding of theinside surfaces of blades Mil whose inside surfaces are of zeropressureangle. 7 A conical grinding wheel M! -is used Fig. illustrates a methodfor axially. reliefwhose axis I42 is so inclined to the axis I 8| of theblade-carrying head I02 that the active profile of the wheel will extendin the direction of profile of the inside surfaces of the blades, thatis, be parallel to the axis I02 of the cutter head; The relievingoperation is effected, as before, by rotating the head and wheel ontheir respective axes and producing a reciprocating motion of l in Fig.9. The relief-grinding is eifectedby rotating the cutter head I02 andwheel II on their respective axes while reciprocating the wheel axiallyonce per bladeto be ground asdenoted by the arrow I55.Hereagain'therelieved inside surfaces or the blades will have acombination radial and axial relief. In the method illustrated in Fig.10, however, the wheel moves outwardly during therelieving operation ifthe blade is relieved from ,front to rear whereas in jthe methodillustrated in Fig. 9, the wheel is moved inwardly during relieving ifthe blade is relieved from front to rear. Fig. 11 shows a method forrelief grinding blades ofcurved profile such as may beused-for thecutting of varying-leverage gears'according to the process of mycopending application ;No. 395,072, filed May 24, 1941. Fig. llshows therelieving of the outside blades of this cutter. Here the blades I80 haveoutside surfaces IGI which are of compound profile curvature beingconcave for a portion of their height and convex for the rest of theirheight. These blades are adapted tofinish-cut at onlyone point in theirheight and at that point they are of ,zero or substantially zeropressure angle. Hence the blades require radial relief. This can readilybe produced on the machine of the present invention by using a grindingwheel, such as shown at I62, which is dressed to a profile shapecorresponding to the shape to be ground onthe outside surfaces IBI ofthe blades. This wheel is adjustedso that its axis I63 is inclined-tothe axis I01 ofthe cutter head I92. Relief-grinding is efiected asbefore by rotating the wheel and cutter head on their respective axesand reciprocatingthe wheel axially as indicated by the arrow. I86.Thisreciprocating movement is, as before, in time with the rotation ofthe cutter head and occursyonce for each blade to be ground, being inone: direcs tion during the grinding of the side surface of a blade andin the opposite direction when they side surface has been completed inorder to return the wheel to initial position ready for, the rinding ofthe next blade. Because the axial movement of the wheel is in adirection inclined to the axis of the cutter head, the outside surfacesof the blades will have a combined radial and axial relief and thereforehave the cutting clearance required. x

Fig. 12 shows how the machine of the present invention may be employedfor the grinding of the inside blades I'Ill of a cutter for cuttingvaryingleverage gears according to the process of my application No.395,072 above mentioned. :Here a grinding wheel H2 is usedwhich is.dressed to a profile shape corresponding to the profile shape to beproduced on the blades- This wheel is adjusted so that its axis I13 isinclined to the axis IOI ofthe cutter head I82. Relief-grinding iseffected by rotating the wheel and cutter head on their respective axesand reciprocating the wheel in the direction of its axis, as indicatedby the arrow I16 in accordance with the principle already described withreference to Fig. 11.

Figs. 14 to 19 inclusive illustrate various methods which may beemployed'for relief-grinding race-mill gear cutter blades on the machineof the present invention where the cutter blades are mounted in a dummyhead to extend in the direction of the axis of said head but in offsetposition, that is, non-radially of the axis of that head.

When the outside surfaces of the blades B are to beground by any of themethods illustrated in Figs. 14 to '19 inclusive, each blade is mountedin a dummy head such as denoted at I89 in, Fig. 20. This head isprovided with non-radial blade slots Irll, the center line I82 of eachslot being inclined at an angle C to line I83 radial of the axis I34 ofthe dummy head. The angle 0 is determined by the clearance angle whichit is desired to produce on the sides'urfaces of the blades.

For relief-grinding the inside surfaces of the blades according to anyof the processes illustrated in Figs. 14 L019 inclusive, a dummy head,such as shown at I30 in Fig. 21, is employed. This head has blade slotsIGI which are nonradial or" the axis I98 of the dummy head. Each slot ofthe dummy head ifillhas its center line I92 inclined at an angle 0' to aline I93 radial of the axis Hid oi the head. I The angle C isdeterminedby the clearance angle desired on the inside surface of the blades. Inthe dummy head or either Fig. 20 or Fig. 21, all blades extend in thegeneral direction of the axis of the head and all of the blades, bothinside and out, can be relieved simultaneously. I

Fig. 14 illustrates how the machine of the present invention may beemployed for relief-grinding the outside surfaces of face-mill gearcutter blades according to the known ofiset grinding process. Here theblades 288 to be ground are mounted in a dummy head I80, such as shownin Fig. 20,'and a cylindrical grinding wheel 282 is employed. Thegrinding wheel 202 is inclined to the axis I84 of the dummy head inaccordance with the pressure angle of the blade surfaces to be ground;For the relief-grinding operation, the

wheel and head are simply rotated on their respectiveaxes 2N and I86. Noother motion is required;

Fig. 15 illustrates how the machine of the present invention may beemployed for relief-grindngthe outside surfaces of cutter bladesaccordmg. to a modification of the known offset grinding process. Herethe blades 2W, whose outside 's urfacesare to be ground, are againmounted in a dummy head I and again a cylindrical grinding wheel isemployed. The cylindrical grinding wheel 2I2 is adjusted so that itsaxis 2 is inclined to the axis I84 of the dummy head at the pressureangle of the bladesuriaces to be ground. In;-the relievingoperation, thedummy head I89 and wheel 2 I 2 are rotated on theirrespective axes andin addition a reciprocating movement is effected-axially of the wheel.This reciprocating movement, whichis denoted by the arrow 2I5 isprovided for the purpose of producing a fine finish on the side surfacesof the blades and is preferably so. timedtothecutter rotation that thenum required cutting clearance;-

head I90 such as that shown in Fig; 21; The grinding'wheel 222, which isemployed, isdressed tohave a profile, in the instance shown which is"straight and parallel to the axis 2240f the wheel for the portion225 of;its height and whichi is inclined to the axis of the wheel fortheiportion the-same shape after sharpening .as When new.

Inthe process illustrated inFig;v 19, the Wheel I 252 used-is adjustedso that its axis 254' is in- 226 of itsheight'. The portions 225iand22610? the profile of the wheel are inclined to one another incorrespondence with the inclination of the two, portions of the profileof the inside surfaces of the cutting blades to beground." Forthereliefgrinding operation, wheel and dummy head. are

rotated on their respectivefaxes 224 and l94 and simultaneously an axialreciprocating motion is imparted to the wheel'as denoted byth'e arrow221. This reciprocating motion is in time with the rotation of the head22! and-occurs once for each blade to be ground, the motionbeing in onedirection during actual relief-grinding of theside surface of a bladeand in the opposite direction at the end of the relieving operationtopermit of return of the wheel to initial position ready for relievingthe next blade. I

Fig. 17 illustrates howthe machine of'ithe present invention may beemployed for the relief grinding of the inside surfaces-23l of blades230 whose inside surfaces are'of zero pressure angle. A cylindricalgrinding wheel 232 is used and the wheel is so adjusted that its axis"23ers parallel to the axis lsllof' the dummy head. For the re-'-lief-grinding operation, the wheel and dummy head are simply rotated ontheir respective axes.

No axial motionof the wheelis required. Due to clined tosthe axis 194ofthe dummy head let in which the blades '25!) that are to be "groundare; mounted. Here again, relief-grindingiseffected by rotating thewheel and dumniy head ontheir' respective axes while eiiectin'g zaxialmovement of the wheel. Asbefore, thewheel-is reciproe" cated axially, asdenotedrby'the'1arrow255, once for each blade to; be ground, the axialmovement: s I

being in one direction" during actual. relievingg'off the side surfaceof ablade andbeing in the oppo- "desur face has. been completed in orderto return the I wheel to initial position; ready for grinding the;-

site direction when I the relieving of; the

next blade. As in" themethods illustratedjn Figs. 16 and 18, the axialmovement -of the wheel: in. the method shown Fig. 19 is .for-thepurposeofproducing the same profile s'shapefrOm l fQntto rear, on the sidesurface of the-blade; so; that? the blade will retain its-shape aftersharpening;

While; the invention has [been describediin connection witha particularmachine "emhodi-j Y ment andin connection with severalispecificprocessesfor relief-grinding face-mill cutter blades, it willv be understood thatthemachine isj not restricted tofluse with thevarious processes thenon-radial arrangement of'the inside surfaces of the blades in'thedummyhead, radial re lief will be produced on the side surfaces 'o'f'theblades back of their cutting edges to provide'th'e Figs. 18 and 19illustrate two novel Waysin;

' which the machine of the present-invention may be employed for therelief-grinding of the inside surfaces of blades, of compoundcurvaturesuc'h,

as may be used in cutting varying-leverage gearsaccording to theinvention of my co-pending-application, Serial No. 3951372, abovementioned.

In both cases, a grinding Wheel is employedwhich has its active surfacedressed to'a profile shape corresponding to the shape which it; isdesired to produce on the'inside surfaces of the blades.

In the method illustrated in Fig. '18, the Wheel 242 is adjusted so thatits axispzd is parallelto' the axis IS4 of the dummy head i 90 in whichthe:

blades 2% that are to be ground are mounted. Relief-grinding is hereei'lcctedfiby rotating the dummy head and wheel on their respective axeswhile moving the wheel axially. "The "wheelds reciprocated, asindicatedb'y the arrow 245, in

time with the rotation of'the dummy head, the wheel being'moved axiallyin onedirectionduring the actual grinding of the side surface of a bladeand being movedaxially inthe oppositedirection at the end of eachgrinding operation to return the wheel to initial position. a Thei'axial/move ment is required to insure that the same profil'e Tcurvature will be produced on the side surfaces-f the blades at allpoints of the length-oftheblad'es described. This application isintended to cover any variations, uses, or adaptations of the invention,following, in general, the principles of the. invention andincludingsuch departuresfr'om the present disclosure as comewithinknownor customary practice in the gear'art andas maybe applied tothe essential featureshereinbefore Sal j I, forth and as fall within thescope of the inven l' tion or the limits of the appended claims.

' Havingthus described myinventiom,what gl I 1. In a machine:forrelieving face-mill cutter; blades whose side surfaces havedifferentinclina-k o I tionsto the cutteraxis at -difierentpoint-alongtheir heights; a. rotary Work support,; a rotarytoolspindle,having its axis inclinedtothe axi of the work support, a rotary :toolmounted on, the tool spindle'and having an axial profile which isofdifferent inclination to the .tool axis'at'differentpoints in theheight ofthe profile; means for rotating thework support, means forrctat- 3 ing the tool spindle, and'means for efiecting, a

relative reciprocatory movementflbetween the tool spindle and worksupport axially 'OffllhE-JllQOl I spindle and in time with the rotationofthe work] support once for each blade to berelieved during I eachrevolution of the, work support-the forward I portion ofeachreciprocatory movement serving in conjunctionwith the rotation ofthe workJsupport to effect relieving of a blade surface and the returnportion of each reciprocatory movement serving to reposition the tooland work sup ort relative to onea'nother'readyfor the'relieving ofthe'next'ibl'ade. f Y a,

2. In a machine for relieving race-min cutter blades, a rotary worksupport,- apair of rotary tool spindles, rotary tools mounted thereontorelieve,respectivelnthe outside and'insidesurfaces I of cutter blades;means for adjusting the; tool spindles angularly to inclinetheir axestothe axis of the work. support, means'for rotatingfthe work support onits axis,'me'ans for'rotatingthe tool spindles 'ontheir respective axes,and means I for reciprocating each toolspindle axially in its. angularlyadjusted position in time with the TO-r:

tation of thework supportand once for'each:

from front togrear so that the bladesmay have 'lade to be relieved oneach revolution of the work support to effect relief of a, side surfaceof a blade on axial movement of a tool spindle in one direction and toreposition the tool spindle for relieving of the next blade' on axialmovement of the tool spindle in the opposite direction.

3. In a machine for relieving face-mill cutter ally in time with therotation of the work support once m each blade to be relieved on"eachTeVolution of the work support; so as to effect relief ofsuccessive blades of'the cutter.

4. In almachine for relieving side surfaces of blades of a sphericalface mill gear cutter, a rotary work support, a blade carrying headsecured thereto and having the blades carried thereby tipped forwardlyout of cutting position, a rotary tool spindle having its axis inclinedto the axis of.

thework support, a rotary grinding wheel se cured to the tool spindleand having an active surface of circular arcuate profile in an axialplane, means for rotating the work support on its axis, means forrotating the tool spindle on its axis, andmeans for reciprocating thetool spindleaxially in time with the rotation of the work support.

;5. In a machine for relieving face-mill gear cutter blades, a rotarywork support, a rotary tool spindle havingits axis inclined at an angleto the axisof the work support, a rotary tool secured to saidtoolspindle, means for-"rotating the work support continuously, meansfor rotating the tool spindle, a cam having an operative connection withthe 'tool spindle, means for rotating the cam continuously in time withthe rotation of the worksupport to reciprocate the tool spindle axiallyin time with the rotation of the work support and once for each blade tobe ground per revolution of the work support, and means for varying thestroke of the tool spindle.

6. In a machine for relieving face-mill gear cutter blades, a rotarywork spindle, a rotary tool spindle, a rotary tool se'cured'to said toolspindle,

means for rotating the work spindle, means for rotating the toolspindle. and means for axially reciprocating one of said spindlescomprising a bar having an operative connection with said spindle,'arotary cam, a; secondbar having an op-- i spindle. a rotary tool securedto said tool spindle,

means for rotatingthework spindle, means for rotating the tool spindle.and means for axially reciprocating one of said spindles comprising abar having an operative connection with said spindle, a pair of parallelsupports pivotally connected to said bar, a pivoted arm slidablyadjustable with reference to each of said supports, a

. said second bar, and means for rotating said cam in time with therotation of the work spindle. 8. The method of relieving the sidesurfaces of face-mill gear cutter blades whose side surfaces havedifferent inclinations to the cutter axis at different points alongtheir heights, which compn'ses mounting the blades in a rotary head sothat they are arranged circularly about the axis of the head and extendin the general direction of said axis, engaging a rotary grinding wheel,whose profile is of different inclination to the axis of the wheel atdifferent points in the height of the profile, with the side surface ofa blade to be relieved with the axis of the wheel inclined to the.axis'of the head atan angle equal to the pressure angle of the side ofthe blades to be relieved, and rotating the wheel and head on theirrespective axes while effecting a relative reciprocatory movementbetween the wheel and head'axially of the wheel in time with the headrotation and once for each blade to be relieved on each revolution ofthe head to relieve the side surface of a blade on the forward portionof each reciprocatory movement and to reposition the wheel and headrelative to one another ready for the relieving of a. side surface ofthe next blade on the return portion of each reciprocatory movement.

9. The method of relieving the side surfaces of face-mill gear cutterblades which comprises mounting the blades in arotary head so that theyare arranged circularly about the axis of the head and extend in thegeneral direction of the axis of the head but are offset sidewise fromthe positions which they occupy during cutting so as to be non-radial ofsaid axis, engaging a rotary grinding wheel, whose profile is of varyinginclination to its axis, with the side surface of a. blade so that theaxis of the wheel is inclined to the axis of the head at an angle equalto the pressure angle of the side of the blades to be relieved, androtating the wheel and head on their respectiveaxes while reciprocatingthe wheel axially in time with the head rotation once for ea ch blade tobe relieved on each revolution of the head whereby to relieve a sidesurface of a blade from front to rear on the forward portion of eachreciprocatory movement of the wheel and to reposition the wheel readyfor relieving the next blade on the return portion of each reciprocatorymovement.

10. The method of relieving side surfaces of face-mill ear cutter bladeswhose profiles have varying inclination to thecutter axis at differentpoints in the blade height, which comprises mounting the blades in arotary head so that they are arranged circularly about the axis of thehead and extend in the general direction of said axis but are oiisetsidewise from the positions which they occupy during cutting so as to benonradial of the axis of the head, employing a rotary grinding wheelwhose profile in an axial, plane is similar to the profile of the bladesurfaces to be relieved and has a varying inclination to the wheel axisat difierent points in its height, engaging said Wheel with the sidesurface of a blade. and rotating the wheel and head on their respectiveaxes while reciprocating the wheel in the di rection of its axisin timewith the head rotation and oncefor each blade to be ground on eachrevolution of the head.

11. The method of relieving side surfaces of face-mill gear cutterblades whose profiles have relieved and has varying inclination to thewheel axis at different points in its height, engaging said wheel withthe side surface of a blade with the axis of the wheel inclined to theaxis of the head and lying in the same plane as the axis of the head,and rotating the wheel and head on their respective axes whilereciprocating the wheel in the direction of its axis in time with thehead rotation and once for each blade to be round on each revolution ofthe head.

ERNEST WIIDHABER.

